Ann and David Collins hold one of their missing posters during a news conference March 2, 1984 in San Francisco,. Their son, 10-year-old Kevin Collins, disappeared Feb. 10 while returning home from basketball practice.

Photo: Paul Sakuma, Associated Press 1984

Ann and David Collins hold one of their missing posters during a...

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A memorial service for Kevin Collins was held on the 10th anniversary of his disappearance at Holy Cross Cemetery in Colma on Feb. 10, 1994.

Photo: BRANT WARD, Brant Ward, The Chronicle

A memorial service for Kevin Collins was held on the 10th...

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During a memorial service for Kevin Collins on the 10th anniversary of his disappearance, a bench with his inscription was unveiled at the Holy Cross Cemetery in Colma on Feb. 10, 1994.

Photo: BRANT WARD, Brant Ward, The Chronicle

During a memorial service for Kevin Collins on the 10th anniversary...

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Officer Chris Porter leaves the home 0n Masonic Avenue that police searched for evidence in the Kevin Collins case.

Photo: Mathew Sumner, Special To The Chronicle

Officer Chris Porter leaves the home 0n Masonic Avenue that police...

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Michael Scharff, who knew Kevin Collins, stands in front of the house on Masonic Ave. where an investigation of the 1984 disapperence of, then, 10- year-old Kevin takes place on Tuesday, January 29, 2013.

Photo: Mathew Sumner, Special To The Chronicle

Michael Scharff, who knew Kevin Collins, stands in front of the...

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A public works employee exits a walkway at the house at 1108 Masonic Ave. where an investigation of the 1984 disapperence of 10- year-old Kevin Collins takes place on Tuesday, January 29, 2013.

Photo: Mathew Sumner, Special To The Chronicle

A public works employee exits a walkway at the house at 1108...

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Officer Pam Cunningham, right, photographs an item held by another officer related to the investigation of the 1984 disapperence of 10- year-old Kevin Collins on Masonic Ave. on Tuesday, January 29, 2013.

Photo: Mathew Sumner, Special To The Chronicle

Officer Pam Cunningham, right, photographs an item held by another...

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Officer Pam Cunningham exits 1108 Masonic Ave. while on an investigation related to the 1984 disapperence of 10- year-old Kevin Collins on Tuesday, January 29, 2013.

Photo: Mathew Sumner, Special To The Chronicle

Officer Pam Cunningham exits 1108 Masonic Ave. while on an...

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San Francisco Police park a mobile command vehicle in front of a home on the 1100 block of Masonic Avenue Tuesday Jan. 29, 2013 in San Francisco, reportedly looking for evidence in the disappearance of 10-year-old Kevin Collins 29 years ago. A law enforcement official tells The Associated Press that investigators were digging in the backyard and the basement of the home near the city's Haight-Ashbury district Tuesday. (AP Photo/San Jose Mercury News, Karl Mondon) MAGS OUT; NO SALES; NO INTERNET USE

Federal and local law enforcement officers searched a home in San Francisco's Haight-Ashbury neighborhood Tuesday as part of a renewed probe into the 1984 disappearance of 10-year-old Kevin Collins, but found little except apparent animal bones, authorities said.

Cadaver dogs brought in by San Francisco police and the FBI detected remains under the concrete floor of the garage in the duplex at 1106-1108 Masonic Ave., a block from where the boy was last seen, police said. Authorities had the floor jack-hammered, but what they found appear to be the bones of an unidentified animal, police said.

Further tests will be done to confirm the source of the remains, police said.

Kevin was the first of a string of Bay Area children who vanished in the 1980s and early 1990s and never came home. A photo of his freckled face was among the first to be widely featured on milk cartons in an effort to publicize missing-children cases.

Hard for family

His parents long ago reconciled themselves to the likelihood that he is dead, but Tuesday's renewed search was wrenching all the same.

"I feel numb," said Kevin's mother, Ann Collins, 72, who now lives in Concord. "I hope I can sleep tonight."

Kevin disappeared on his way home from basketball practice at St. Agnes School on Feb. 10, 1984. He was last seen on a bus bench at 6:40 p.m. at Oak Street and Masonic Avenue, half a block from the school.

No solid suspect ever emerged. The closest lead anyone had was a report that, around the time he was presumably snatched, Kevin was talking to a tall, blond man with a large black dog.

The home that was searched Tuesday is a block south of Oak and Masonic. The current occupants are not suspects, police said in a statement, but a law enforcement source said a man who used to live there had been a person of interest in the case.

The man, who has since died, was never arrested. Police investigators who recently reviewed the cold case decided that he matched the general description of a man who might have been seen talking to Kevin, and noticed that when his home was searched at the time, cadaver dogs had not been used.

Dogs from the Alameda County Sheriff's Department were brought in for Tuesday's search, which lasted most of the day.

A neighbor, Michael Scharff, 72, said the former resident had run a motorcycle business out of the home's garage.

'Time for it to be over'

Ann Collins said part of her wanted the mystery resolved, and part did not.

"It's a very strange thing," she said. "Two or three of my boys have called and said, 'Mom, it's time for it to be over.' It would be nice to have closure, but at the same time not."

She added, "Maybe for me and my children and my grandchildren, it's better to have closure and go on with our living. But sometimes, I think it would be better not knowing."

Kevin Collins would have turned 39 last week. Ann Collins said her son loved doing things with his hands. The other day, a TV commercial showing a man working under a car made her think of him - and the future he never got to live.

"That's the hard part - he was only 10," she said. "We didn't have him long enough to know" what he could become.